Self-reported and measured weight, height and body mass index (BMI) in Italy, the Netherlands and North America

TLDR

Self‑reported height and weight are widely used but are known to be biased. The study examines whether discrepancies between self‑reported and measured values differ by region, gender, and age. Researchers compared self‑reported and measured weights, heights, and BMIs in representative adult samples from Italy, the Netherlands, and North America. Weight was under‑reported and height over‑reported, causing BMI underestimation and misclassification of 11–12 % of adults, with larger errors in Italian females, and differences varied by country, gender, and age.

Abstract

Background: Self-reported values of height and weight are used increasingly despite warnings that these data—and derived body mass index (BMI) values—might be biased. The present study investigates whether differences between self-reported and measured values are the same for populations from different regions, and the influences of gender and age. Methods: Differences between self-reported and measured weights, heights and resulting BMIs are compared for representative samples of the adult population of Italy, the Netherlands and North America. Results: We observed that weight is under-reported (1.1 ± 2.6 kg for females and 0.4 ± 3.1 kg for males) and height over-reported (1.1 ± 2.2 cm for females and 1.7 ± 2.1 cm for males), in accordance with the literature. This leads to an overall underestimation of BMI values (0.7 ± 1.2 kg/m2 or 2.8% for females and 0.6 ± 1.1 kg/m2 or 2.3% for males). When BMI values are assigned to four categories (from 'underweight' to 'obesity'), 11.2% of the females and 12.0% of the males are categorized too low when self-reported weights and heights are used, with an extreme of 17.2% for Italian females. Older people tend to relatively over-report height and under-report weight, but the magnitude differs between countries and gender. Conclusion: We conclude that, apart from a general overestimation of height and underestimation of weight resulting in an underestimation of BMI, substantial differences are observed between countries, between females and males and between age groups.